peter
e995c664c6
GET /api/channels summed every subscribed channel's videos by reading each video's heap page (681 MB on prod): 51-61 ms warm, but 2.25 s on a first open and 6.4 s under EXPLAIN once the table had left memory. /feed/summary and /feed/years did the same (~140 ms warm, ~800 ms cold). Migration 0095 replaces ix_videos_channel_pub_desc with the same key INCLUDING the columns those queries read, so they are Index Only Scans over a 25 MB index. A test holds the queries and the index's column list together. The admin Configuration page did a db.get per setting (two for an unset one): it now reads every override in one query (~40 ms of ~55 on prod).
40 lines
1.5 KiB
Python
40 lines
1.5 KiB
Python
"""The admin Configuration page reads every override in one query (E31 S4d).
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`sysconfig.describe()` did a `db.get` per key to tell whether an override was set, and `get()` did one
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more for its value: ~55 keys, and two round trips for a key with no row, since the session cannot cache
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an absence. That was ~40 ms of the page's ~55 on prod. It now reads the table once. DB lane.
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"""
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from sqlalchemy import event
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from app import sysconfig
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def _statements(db, fn) -> int:
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seen: list[str] = []
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engine = db.get_bind()
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listener = lambda *a, **k: seen.append(a[2]) # noqa: E731 — (conn, cursor, statement, …)
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event.listen(engine, "before_cursor_execute", listener)
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try:
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fn()
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finally:
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event.remove(engine, "before_cursor_execute", listener)
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return len(seen)
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def test_describe_reads_the_overrides_once(db):
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sysconfig.set_value(db, "quota_daily_budget", 5000)
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db.commit()
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assert _statements(db, lambda: sysconfig.describe(db)) == 1
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def test_describe_shows_the_stored_value_and_the_default(db):
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sysconfig.set_value(db, "quota_daily_budget", 5000)
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db.commit()
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items = {i["key"]: i for g in sysconfig.describe(db)["groups"].values() for i in g}
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assert items["quota_daily_budget"]["is_set"] is True
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assert items["quota_daily_budget"]["value"] == 5000
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other = next(i for k, i in items.items() if k != "quota_daily_budget" and not i["secret"])
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assert other["is_set"] is False
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assert other["value"] == other["default"]
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